RU2538099C2 - Lamp exciting method and device - Google Patents

Abstract

FIELD: electricity.

SUBSTANCE: invention relates to lighting engineering. The lamp exciting method and device (2) includes stages whereat: electric current of the lamp is generated (Iconst) with constant value; commutation period is preset with duration equal to Tcomm; time-base sweep is preset for initial moments of commutation with fixed mutual intervals of 0.5xTcomm; data to be outputted at the light output are received; electric current of the lamp is commutated at commutation moments; at that separate commutations are time-modulated in order to code the above received data. The commutation moment shall be preferably: either equal to the initial moment of commutation when there are no data to be outputted or advanced per modulation interval (Δ) in regard to the respective initial moment of commutation for coding of data having the first value ("0") or delayed per the above modulation interval (Δ) in regard to the respective initial moment of commutation for coding of data having the second value ("1").

EFFECT: increased data processing rate during data coding to output light generated by the lamp.

15 cl, 6 dwg

Description

FIELD OF THE INVENTION

The present invention generally relates to the field of lamp excitation technology. The present invention relates, in particular, but not exclusively, to the field of excitation lamp technology, and hereinafter the invention will be explained for the case of high intensity discharge lamps (HID).

BACKGROUND OF THE INVENTION

Various forms of electric current signal are possible to excite a light source. Incandescent and some types of discharge lamps may be excited by alternating current, and LEDs (LEDs) may be excited by direct current. Typically, HID lamps are energized by DC switching; this means that the magnitude of the electric current is constant, but the direction of the electric current is regularly reversed. Since it is desirable that the average value of the electric current is zero, the duration of the passage of electric current in one direction is equal to the duration of the passage of electric current in the opposite direction. In other words: in a period of electric current, an electric current flows in one direction for 50% of the period and passes in the other direction for the remaining 50% of the time. Since such a switching current is known per se, a further description thereof will be omitted herein.

In general, the developer has some freedom to choose the frequency of the electric current. However, there are some limitations. Low frequencies, such as less than 100 Hz, can cause visible flicker. At higher frequencies, acoustic resonance can lead to damage to the lamp, so that the operating frequency must be chosen in the frequency range in which, presumably, acoustic resonance will not occur. Of course, these ranges depend on the type of lamp.

There is a desire to be able to transmit data using visible light emitted by a lamp. In one example, the transmitted data may refer to a unique lamp identification number so that the receiver receiving the lamp light can identify the lamp that emitted the light. In another example, the transmitted data may relate to lamp parameters such as life, voltage, etc., so that technicians can check the condition of the lamp and decide to replace the lamp without actually having to approach and inspect the lamp. It is already known to modulate the lamp electric current to provide “coded light”, but in the case of HID lamps, it is undesirable to modulate the amplitude of the electric current, and the frequency band available for frequency modulation is limited.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a method of encoding data into an output light generated by a light source suitable for use by its HID lamp.

This goal is achieved by the method according to paragraph 1 of the claims.

Further preferred developments are mentioned in the dependent claims.

Brief Description of the Drawings

These and other aspects, features and advantages of the present invention will be further clarified by the following description of one or more preferred embodiments with reference to the drawings, in which the same reference numbers indicate the same or similar parts and in which:

figure 1 schematically depicts a drive circuit for driving a discharge lamp;

2 is a graph schematically illustrating a conventional switching current waveform;

3 is a block diagram schematically illustrating a switch;

4 is a timing chart;

5 is a graph schematically illustrating a conventional switched current waveform with data encoding;

6 is a graph schematically illustrating a switched current with data encoding in accordance with the present invention.

DETAILED DESCRIPTION OF THE INVENTION

1 schematically depicts an example embodiment of an excitation circuit 100 for driving a discharge lamp 2. This embodiment includes an electric current source 110 receiving power from a suitable power source (not shown for simplicity) and capable of generating a constant current Iconst having a predetermined value Im The drive circuit 100 of this embodiment further comprises a switch 120 receiving the Iconst direct current from the current source 110 and designed to repeatedly change the direction of the electric current while maintaining the electric current value Im. It should be noted that other embodiments of the drive circuit are also possible to provide a switched lamp current.

2 is a graph schematically illustrating a conventional waveform of a switched current Icomm provided by a switch 120 to a lamp 2. At time t0, an electric current transitions from a negative direction to a positive direction. Between times t0 and t1, the electric current has a constant value Im and a positive direction, designated as + Im. At time t1, an electric current makes a transition from a positive direction to a negative direction. Between times t1 and t2, the electric current has a constant value Im and a negative direction, designated as -Im. At time t2, the electric current again transitions from the negative direction to the positive direction, and the above steps are repeated. It should be noted that the direction of the current, designated as "positive", and the direction of the current, indicated as "negative", is arbitrary.

In the future, the following definitions will be used:

1) a change in the direction of the current to the opposite, as is done at time t0, t1, t2, will be denoted as "switching"; switching is depicted as inertialess, that is, the duration of the switching process is zero, but in practice switching will take some finite time;

2) time instants t0, t1, t2, when switching occurs, will be designated as “switching moments”;

3) the transition from a positive electric current to a negative electric current will be designated as “negative” switching, and the corresponding switching moments (t1) will be designated as “negative” switching moments; similarly, the transition from a negative electric current to a positive electric current will be designated as “positive” switching, and the corresponding switching moments (t0, t2) will be designated as “positive” switching moments;

4) the frequency of the electric current signal will be indicated as the switching frequency fcomm; its reciprocal will be designated as the switching period Tcomm = 1 / fcomm = (t2-t0);

5) switching divides the switching period into two temporary switching segments, that is, into a “positive” temporary switching segment having a duration tp = (t1-t0) between the positive switching moment and the subsequent negative switching moment, and a “negative” temporary switching segment having the duration tn = (t2-t1) between the negative switching moment and the subsequent positive switching moment; it should be clear that Tcomm = tp + tn.

Traditionally, tp = tn = 0.5 × Tcomm; it should be clear that, therefore, the average value of the electric current is zero (without a constant (DC) component of the current).

3 is a block diagram schematically illustrating a possible embodiment of a switch 120; it should be noted that other embodiments of the switch are also possible. The switch 120 includes two power lines 121 and 122 that receive Iconst direct current. The first series connection of two controllable switches 123, 124 is connected between power lines 121 and 122, with a first node A between them. A second series connection of two controllable switches 125, 126 is connected between power lines 121 and 122 with a second node B therebetween. A lamp 2 is connected between the aforementioned nodes A and B. The switches 123, 124, 125, 126 are controlled by a control device 130, for example, a suitably programmed microprocessor or controller that can operate in one of two states: in the first state, the switches 123 and 126 are conductive, while the switches 124 and 125 are non-conductive so that the electric current passing through the lamp flows from A to B; in the second state, the switches 123 and 126 are non-conductive, while the switches 124 and 125 are conductive so that the electric current passing through the lamp flows from B to A. It should be clear that these two states of the controller correspond to the aforementioned time segments commutation. In addition, it should be clear that the timing of the transition from the first state of the controller to another or vice versa determines the timing of the switching times.

The control device 130 is provided with a synchronization device 150 providing a synchronization signal Sc for setting a time base corresponding to the switching frequency fcomm. This time scan allows the control device 130 to determine switching times. For clarity, the synchronization device 150 is depicted as being outside the control device 130, but it can also be integrated into the control device 130.

FIG. 3 also schematically depicts a receiver 200 configured to receive light emitted by a lamp 2. Note that the receiver 200 is capable of detecting switching times, as will be explained with reference to the timing diagram of FIG. 4, curve 41 shows the switching current of the lamp. Curve 42 depicts the corresponding power supply of the lamp and depicts power failures that coincide with the moments of switching, since switching cannot be inertialess. Curve 43 depicts the corresponding output light level and also depicts dips corresponding to power failures, although not necessarily falling to zero in view of the intrinsic inertia of the physical properties of the lamp. From figure 4 it should be clear that the frequency of light dips is twice as high as the frequency of the electric current of the lamp. Receiver 200 will be able to detect light intensity dips, as one of skill in the art would understand without the need for further explanation.

Note that the receiver 200 cannot distinguish between the light generated by the positive electric current and the light generated by the negative electric current. Therefore, the receiver 200 cannot directly identify the positive switching points and the negative switching moments.

In accordance with the present invention, the driving circuit 100 is capable of encoding data in the output light of a lamp by modulating the timing of the switching times. To this end, the control device 130 has a data input device for receiving binary data from a data source 140 (FIG. 3); the nature of the data source is irrelevant, but for example, the data source 140 may include a storage device containing an identification number. The control device 130 is designed to change the timing of the switching times depending on the current data bits. In general, this principle is also known. 5 is a graph illustrating a coding scheme proposed earlier.

For encoding a bit having a value of "0", the timing of the switching moments is set so that within one period of the electric current, the duration of the positive segment of the positive time segment of the switching has a value of tp0, and the negative duration of the segment of a negative time segment of the switching has a value of tn0, and tp0 = tn0. For encoding a bit having a value of "1", the timing of the switching moments is set so that within one period of the electric current, the duration of the positive segment of the positive time segment of the switching has a value of tp1, and the duration of the negative segment of the negative time segment of a switching has a value of tn1, and tp1 = tn1. In addition, tp0 = tn0 ≠ tp1 = tn1: in the illustrated example, tp0-tn0 <tp1 = tn1. Therefore, Tcomm, 0 <Tcomm, 1. The advantage of this earlier coding scheme is essentially that the average value of the electric current is always zero. Another advantage is that it is relatively easy for the receiver to recognize periods of electric current, and the disadvantage is that it is more difficult to actually synchronize with periods of electric current. In addition, the inconvenience is that the data processing speed f = 1 / Tcomm depends on the information content of the data.

The present invention provides a data coding scheme in which Tcomm is constant so that the data processing speed f = 1 / Tcomm is independent of the information content of the data. FIG. 6 is a graph comparable to FIG. 5 illustrating an example data encoding scheme in accordance with the present invention. To encode a bit with a value of "0", the timing of the switching moments is set so that within the same period of the electric current with a duration of Tcomm, the duration of the positive segment of the positive temporary switching segment is tp0 = 0.5 × Tcomm-Δ, and the duration the negative segment of the negative time switching segment had the value tn0 = 0.5 × Tcomm + Δ. To encode a bit having a value of "1", the timing of the switching moments is set so that within one period of the electric current with a duration of Tcomm, the duration of the positive segment of the positive time switching segment is tp1 = 0.5 × Tcomm + Δ, and the duration the negative segment of the negative time segment of the switching had a value of tn1 = 0.5 × Tcomm-Δ.

The advantage of this circuit is that the periods of electric current always have the same duration. This simplifies synchronization for the receiver 200, since the time interval between the light failure and the subsequent second must always be the same if the drops coincide with the boundaries of the period.

It should be noted that now the average value of the electric current of one period of the electric current depends on the information content of the data. However, over a large time period, the average value of the electric current can again be equal to zero if the number of zeros in a given period of time is equal to the number of units. Of course, in the incoming data stream it is impossible to guarantee that the number of zeros will be equal to the number of units in any time interval, while it is desirable that the average value of the electric current be with great confidence equal to zero in a relatively short time period. To guarantee this, the control device 130 is designed to convert incoming data bits into outgoing transmission bytes, each outgoing transmission byte, which may contain any suitable even number of transmission bits, contains 50% zeros and 50% units. For example, in a simple embodiment, the input bit 0 can correspond to the byte of the outgoing data 01, while the bit of the input data 1 can correspond to the byte of the outgoing data 10: in this case, the average value of the electric current is always zero in the time interval corresponding to two periods of electric current. Other, more complex conversion schemes are possible, allowing the average value of the electric current to be equal to zero over several large time periods, as should be clear to a person skilled in the art. Examples of such schemes are block Walsh-Hadamard codes or block codes with a restriction between transitions in coding.

In the aforementioned embodiment, the periods of electric current are set between two successive positive switching moments, while the modulation of the time reference of the negative switching moments is performed using + Δ or -Δ in accordance with the data bit to be encoded. It is also possible to set the periods of electric current between two consecutive negative switching moments, while the modulation of the time reference of the positive switching moments is performed.

In the above embodiment, the modulation of the time reference of the switching moment within the period of the electric current is performed using + Δ or -Δ in accordance with the data bit to be encoded. In other words, the time reference of this switching moment is shifted relative to its normal, unmodulated time reference, which is 50% of the period of the electric current. In the following description, the offset interval relative to the normal, unmodulated time reference will be referred to as the modulation interval. The modulation interval is set to be positive if the modulation implies a delay, or negative if the modulation implies a lead.

In the above embodiment, the absolute value of the modulation interval can have only one value so that it is possible to encode one bit of transmission data in one period of electric current. It is also possible to allow a plurality of possible values for the absolute value of the modulation interval in order to be able to encode multiple bits of transmission data in one period of electric current. For example, modulation intervals of -2Δ, -Δ, + Δ, + 2Δ can encode two bits (00, 01, 10, 11) for one period of electric current.

In the aforementioned embodiment, only half of the switching moments (negative switching moments) is modulated in time, while the other half of switching moments (positive switching moments) are not. In the above explanation, the switching moments that are modulated are explained as modulation moments that are located at 50% of each period, while the periods are explained as given by the unmodulated switching moments. However, this is not necessary. As explained above, the control device 130 has an available synchronization signal Sc, which allows you to set the time base of the initial unmodulated switching moments having fixed mutual intervals equal to 0.5 × Tcomm. Considering this time base as a reference, it is possible to perform modulation in time of the negative switching moments, as well as the positive switching moments. This will double the data processing speed.

To simplify the synchronization of the receiver 200, it is preferable that, at regular time intervals, a fixed combination of data is included in the data stream known to the receiver. For example, such a combination of data may include a series of sequences “01”.

In conclusion, the present invention provides a method for exciting a lamp 2, which method comprises the steps of:

generate an electric current Iconst lamp having a constant value;

set the switching period having a duration of Tcomm;

set a time scan of the initial moments of switching having fixed mutual intervals of 0.5 × Tcomm;

receive data that must be embedded in the light output;

switch the electric current of the lamp at the moments of switching;

moreover, individual switching modulate in time to encode the mentioned received data.

Preferably, the switching point is:

or equal to the initial moment of switching, if there is no data to attach;

or leading by an interval Δ modulation relative to the corresponding initial switching moment for encoding data having a first value of "0";

or delayed by said modulation interval Δ with respect to the corresponding initial switching moment for encoding data having a second value of “1”.

Although the invention has been illustrated and described in detail in the drawings and in the above description, it will be understood by those skilled in the art that such illustration and description should be considered as illustrative and not restrictive. The invention is not limited to the disclosed embodiments; rather, some changes and modifications are possible within the scope of the invention as defined in the appended claims.

Other changes to the disclosed embodiments may be understood and made by those skilled in the art when practicing the claimed invention from consideration of the drawings, disclosure and appended claims. In the claims, the word “comprising” does not exclude other elements or steps, and the plural feature does not exclude the presence of a plurality. One processor or another unit may fulfill the functions of several elements set forth in the claims. The mere fact that certain measures are set forth in mutually different dependent dependent claims does not indicate that a combination of these measures cannot be advantageously used. Any reference position in the claims should not be construed as limiting the scope.

In the above description, the present invention has been explained with reference to block diagrams that illustrate the functional blocks of the device in accordance with the present invention. It should be understood that one or more of these functional blocks may be implemented in hardware, where the functions of such a functional block are performed by separate hardware components, but it is also possible that one or more of these functional blocks are implemented in software, so that the function of such the functional block was performed by one or more program lines of a computer program or a programmable device such as a microprocessor, microcontroller, c Frova signal processor, etc.

Claims (13)

1. A method of exciting a lamp (2), the method comprising the steps of:
generate an electric current (Iconst) of the lamp having a constant value;
set the switching period having a duration of Tcomm;
receive data that must be embedded in the light output of the lamp;
switch the electric current of the lamp at the moments of switching; characterized in that:
set the time base of the switching moments having fixed mutual intervals of 0.5xTcomm;
modulate in time individual switching relative to the starting points of switching for encoding said received data in light with a constant data processing speed. 2. The method according to claim 1, containing stages in which:
calculate the switching moments on the basis of the above-mentioned time base of the initial moments of switching and on the basis of the received data, and the estimated moment of switching is:
or equal to the initial moment of switching, if there is no data to attach;
or ahead of the interval (Δ) modulation relative to the corresponding initial switching moment for encoding data having a first value ("0");
or delayed by said modulation interval (Δ) with respect to the corresponding initial switching moment for encoding data having a second value ("1"). 3. The method according to claim 2, in which the interval (Δ) modulation has one fixed value in order to be able to encode one bit at the time of switching. 4. The method according to claim 2, further comprising the step of selecting a modulation interval (Δ) value from a predetermined range of possible values in order to be able to encode multiple bits at the time of switching. 5. The method according to claim 1, in which every second switching moment always coincides with a time base, while only the switching moments between said second switching moments are modulated in time. 6. The method according to claim 1, in which all the switching moments are modulated in time independently of each other. 7. The method according to claim 1, in which a series of one or more received data bits are converted into a packet containing an even number of outgoing transmission bits, in which in each packet the number of transmission bits with the first value ("0") is equal to the number of transmission bits with the second value ("1") and in which the modulation of the switching moments is always based on the transmission bits. 8. The method according to claim 1, further comprising the step of regularly inserting a predefined sequence of data, which leads to a predefined diagram of the switching moments to simplify synchronization in the receiver (200). 9. The method of claim 1, wherein said data to be included includes an identification code of the corresponding lamp. 10. An excitation circuit (100) for exciting the light source (2), comprising an electric current source (110) for producing direct electric current (Iconst) and a switch (120) for switching this electric current, the excitation circuit designed to perform the method according to any from claims 1 to 9. 11. A receiver (200) for receiving light emitted by a lamp (2) excited by an excitation circuit according to claim 10, wherein the receiver is designed to recognize intensity dips in the received light intensity, to restore a time base with mutually equal time intervals based on time reference intensity dips, to calculate the time difference between the individual intensity dips and the reconstructed time base and to decode the transmitted data based on the calculated time differences. 12. The receiver according to claim 11 for interacting with an excitation circuit performing the method of claim 8, wherein the receiver is designed to synchronize the reconstructed time base based on a predetermined diagram of intensity drops corresponding to said predefined diagram of switching moments. 13. A system comprising a plurality of lamps (2) excited by a corresponding plurality of driving circuits (100) in accordance with claim 10 and at least one receiver (200) in accordance with claim 11 or 12, wherein each driving circuit performs The method according to claim 9, wherein the receiver is designed to receive light from at least one lamp and to identify a lamp emitting received light based on a decoded identification code.

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